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"From its chamber comes the whirlwind, and cold from the scattering winds." - Job 37:9.

"The wind blows to the south and turns to the north; round and round it goes, ever returning on its course".

Friday, October 22, 2010

(*Image -current forecast track from the NCEP model ensemble guidance from last nights collaboration of data)

SYNOPSIS: "A Nation Divided" Today - Large high pressure from James Bay extends south across the eastern half of the U.S. this morning and into the Bay of Campache at the surface. In the mid-levels a trough persists over New England and SSE into the off-shore mid-Atlantic waters. Further west, a somewhat complex, broad area of low pressure reigns supreme in association with the slow moving mid-level cut off low which has been mentioned for several days since its conception off the N. California Coast last weekend. The low tracked south, into the N. Baja, across Arizona and SW New Mexico, and is now filling and lifting north into Colorado.

At the surface, a dry-line (boundary between deep, moist Gulf air being advected north around the back of the large high pressure area to the east and drier air trying to push east from the Desert SW) will be enhanced this afternoon with day time heating and extend by late day down west Texas, Oklahoma, and SW Kansas (see image from the 22/00z NAM)In this image we can also see the dry air across the eastern U.S. under the high pressure. Florida remains in much more moist air mass in comparison. As you can see, other than the South/Central Plains and Florida late afternoon dew points will be quite low nation wide.

Tropical Storm "Richard" remains nearly stationary in the Caribbean. This will be further discussed in "The Tropics" further within this post.

TODAY: The Plains low pressure area will lift only slightly north and a bit east today and tomorrow as high pressure rides across the Southeast states responds by moving east and eventually into the Western Atlantic over night Sunday into Monday.

Florida remains somewhat in a somewhat 'atmospherically dehydrated' state other than having some comfortable humidity levels at the ground where we feel it. Not too humid, but not too irritatingly dry either. Afternoon warmth could induce some scattered clouds, but no rain. Pleasant temperatures once again with highs in the low 80s from US1 to A1A up and down the east coast, and in the mid-80s west of I-95.

Meanwhile, severe weather potential exists once again east of the dry line over much of South Central Texas, Oklahoma, and West Central Kansas. A mid and upper level jet streaks may cross the dryline later today and into the deep moisture field influx from the Gulf resulting in rising, moist air currents and shear profiles sufficient for development of supercell thunderstorm structures. Five tornadoes were officially reported during the course of yesterday with one in Arizona and other in SE New Mexico (as thought would be possible) with another in SW Texas near Rankin. There were multiple hail reports along the dry-line boundary mentioned above.

SATURDAY-SUNDAY: Not much change locally as the high pressure center begins to move offshore and starts to move more toward the ESE underneath the trough running down the mid-Atlantic Coast mentioned earlier. As such, our winds veer throughout the weekend from predominantly a NE component by this afternoon to east and then eventually ESE-SE by sunset Sunday. Temperatures remain warmer during the afternoons away from the coast, and warmer in the mornings than inland areas overnight.

In the Plains, the mid-level low and associated features begin to elongate and diffuse somewhat. As was expected in the post two days ago, the severe threat for Saturday now looks much larger than what was earlier officially predicted, courtesy of the long-term presence of low pressure and Gulf moisture into the Central Plains from Iowa, through Missouri, extreme eastern Kansas, Oklahoma and East Central Texas ahead of a developing frontal boundary.

MONDAY: Modified late summer-like weather returns to the sunshine state! Surface winds veer even more toward the SSE-SSW during the say at the surface and mid-levels advecting moisture residing over the Southern Bahamas across Florida. Modified because it's now late October and the days are shorter. Also, the moisture will take a while to fully encompass all levels of the atmosphere sufficiently, but by mid-afternoon much of the state will be primed under full, mid-fall sunshine with no capping mechanisms in place to abet in shower and/or thunderstorm development. Caveat. Ocean and lake water temperatures are cooler now than in summer and early fall; as such, collision boundaries won't have the effect they would have under otherwise the ideal conditions for storm development seen in the summer months. Regardless, sufficient heating, moisture, and little to now 'atmospheric lid' should allow cloud tops to percolate vertically to the point of super-saturation. This might be the break we've needed.

TUESDAY: Better yet. More of the same as somewhat deep SSW-SW flow remains one more day and warmer temperatures than what we've felt for quite some time now prevail. We could be feeling like we've gone back in time by Tuesday to the pre-Storm Paula Era, not quite, but kind of close. Steering currents mainly from N. Palm Beach County to Jacksonville will advect activity toward the east coast where drought conditions ranging from moderate-severe officially now exist. Broward County and points south will be close to, if not south of the northward moving ridge axis by days end, thus precluding storms down that way. This is all pretty much a new development when push comes to shove, so refinement to the details as far as timing and areas most likely to have a chance of a shower/storm is highly likely in future posts.

WEDNESDAY: Party ends. High pressure to the state's east builds back over the state with the axis running east/west across the Florida/Georgia border with ensuent light, easterly (and cooler) flow once again takes center stage. Like a little jab in the ribs, another area of high pressure builds east from the Southern Plains which at least eliminates passage of a cold front but does put the majority of the state other than the west coast under a much drier and subsident (sinking) air mass at the mid-levels (roughly from 3000-18,000 feet). We'll need to monitor this state of affairs as we head into Monday though, as there still could remain ample moisture for coastal activity from near Vero-Miami in later days. But, days are shorter, water temperatures are cooler now. It's just not like it used to be when otherwise, such conditions would make for a no-brains 'chance of showers' forecast. Even the West side of the state might get dry-hosed given the time of year from getting rain. But they don't really need much over that way anyway.

THE TROPICS: Just my thoughts this morning based on general model consensus, satellite/water vapor analysis, and land-based, forecasted and actual, atmospheric evolutions over North and Central America.

My take is that after the 24 hours of anticipatory excitement related to Richard over before it's even peaked in strength. At least as far as the U.S. is concerned. Note that the storm is small and very disorganized to start with. At this time it really isn't even moving. Very dry air exists to the W-WNW-NW of the system as was the case all day yesterday, but shear is decreasing as was expected would occur. It is just now starting to look better since I last looked, so I'd expect to see the next official statement that comes out from the Hurricane Center indicating a stronger storm with winds of 50-55mph. Eventually, by the time the set up occurs to bring some rain (potentially) to Florida the same set up will force Richard (Tropical storm or hurricane) into somewhere near Honduras or the Yucatan and smack into a wall of building high pressure which will be approaching Western Mexico over the weekend. This area will join forces with high pressure to the north of Richard, closing the gap for any escape it might have had toward the north and into the Southeast Gulf of Mexico. That seems to be the agreement of the GFS and European Ensemble Guidance from last night's run (to name a few). I'm not waiting to see a more recent output since, as of the time of this post, I see now reason to disagree.

Note: The later portions of the projected tracks included in this post, as well as that from the Hurricane Center take Richard into the South Central Gulf. This is quite some time from now, and even if the storm survives a trip across the Yucatan, it will still have to contend with dry air to the north and wind shear if it survives that long. As such, I do not see any direct threat from this storm to the U.S. (other than for "U.S. Interests) where the system crosses due to flooding.

But (!) a prefunctory "however" statement must be made in closing (as usual). "However", moisture from this system as it presumably gets torn asunder could advect toward Florida by late week next week ahead of the next approaching trough which is yet to exist within all realms of reason. The mechanism that will set our next trough up is probably somewhere passing near Typhoon Megi right now...(which will be making a China landfall later today). This storm has dumped up to 40" of rain over the mountainous portions of Taiwan already with flash flooding being the primary threat.